Here is a simple solution to your worries. Try the following steps you will definitely get out of that trouble.
Go to Run
Type gpedit.msc.
A new box will appear
Now select User Configuration >> Administrative templates >> System >> Ctrl + Alt +Delete as shown in the below figure
Then select Remove Task manager which comes in the right hand side menu.
Final step is double click the Remove Task manager option
Now your Task manager is enabled/ repaired and it will work in XP/2000/2003/2000
Now your Task manager is enabled/ repaired and it will work in XP/2000/2003/2000